[Closed] Motorcycle gearing changing sproket size

Powerbands and gearing on motorcycles are pretty well worked out by he manufacturers and make the most of the torque curve. The likelihood is that you'll turn your perfectly serviceable M/C into a complete dog.

It's a well known fact that Ducatis are overgeared to get them through the ride-by noise tests!

I dropped the gearing on my CB500 and on my Monster 696, but just by one tooth at the front (Because it's the cheapest way of doing it - £15-ish)

And it definitely makes a difference for the better I think on the bikes I've had.

I wouldn't bother faffing with changing both sprockets, just get a 1t smaller front and give it a go! 🙂

(I don't think what you're suggesting will make much difference TBH. It's not as big a change as 1t off the front, and that's not a massive difference, it just adds a dose of perkiness to the acceleration)

I kow what your getting at but I use it for commuting and am interested in the motorway crusing speed. I dont cane the crap out of it.or race everything else on the road. Im tempted tp do it just to find out.

Totally depends on the size of the current sprockets now.

But going down 3 on the back, as well as up 2 on the front, is going to raise the gearing on any bike pretty drastically! You're probably looking somewhere in the region of a 15% decrease in revs for a given engine speed, depending on the bike of course.

Ironically, when Ducati was selling the 916 and the 748, the base model 748 was about as quick under acceleration as the base 916. The 916 was chucking out about 10-15bhp more, but Ducati geared the 916 WAY too high from the factory... It was geared to do 200mph, yet only had the power for about 165... The 748 conversely had the gearing to hit its 160mph top speed perfectly! If course, 916 owners fitted a smaller front sprocket and the bike was loads quicker all of a sudden...

Check you've got crank case clearance to go +2 at the front.

The bike is a 600 bandit, Its not the most powerful but it moves when i want it to. So 15% drop in revs for the relative speed is acceptable.

I took one tooth off the front sprocket of both our Ducati's, made them much smoother around town and generally more ridable.
One off the front is the same as three on the back by the way (usually).

A bit lost of why you'd change both?

Plus as said, watch the clearances - most decent sized bike engines will pull higher gearing.

Mine is geared for 90mph at 5000rpm, well over-geared, yet will pull from 2500rpm in top quite happliy.

i went the other way on the R1 -1 on the front and +1 on the rear, this allowed me to keep the same chain length. the acceleration is properly frightening.

you want to make it higher? Just change up a gear instead...

most go the other way. I went -1 at the front and +2 rear on my gixxer thou 8)

ask on gixerjunkies, they'll know. I used to but it's a while since I've been riding

One tooth on the front is excessive. Two on the front and three off the back is completely OTT. You wouldn't make that big a change on a race bike, never mind a road bike.

Try dropping two off the back and see how you get on.

Leave the front as is and start chopping it down at the rear if you really feel the need.

I went smaller on the front of my Aprilia, they to were geared for noise tests.

The problem could be that you could drop it out of it's optimum power and torque. Lets say that it's geared now to sit at the start of the power/torque starting to really kick in at 70/80mph. Increasing gearing so much could drop it right in to a relatively dead spot so you end up bogging the engine down so you have to change down a gear (or 2) to get any sort of overtaking acceleration. Or you end up in top riding at 90/100 where the engine is now getting lively.

As suggested go for a 1 bigger front first and see how it goes. If you feel it's helped you get where you are heading then maybe go for a front another plus one (if the crank case will take it) or go down 1 or 2 at the back.

The only other way is to get an expert to dyno your engine, discuss what you want to do and take his advice on changing gearing to suit your needs. In my (not expert) opinion this is the only true way that someone could say to you that - if you increase your gearing 12% your bike will be running in an acceptable area of it's power/torque curve and you will reduce your revs by X00rpm and so maybe reduce fuel consumption. Though if you have ever been in a car that displays live fuel consumption you will know that it's when the throttle is opened that fuel consumption goes through the roof.

-1 front here. Best performance mod you can do for the bucks. Reverse of what you want though.

Depends on the bike My old F650 single is well known for having front sproket changes in either direction to give either less teeth loosening on motorways or better acceleration.

more info than you would ever need here:
http://faq.f650.com/FAQs/SprocketsOtherSizesFAQ.htm

If you want to know the affects that changing the gearing will have on the engine rpm/speed try looking on gearing commander:

www.gearingcommander.com

I changed my R1 to -1/+2 gearing and it was mental....completely ridiculous! I eventually went back to standard rear and the -1 on the front.
One thing to remember is that it'll affect your speedo reading on most modern bikes. The R1 was about 16% out from the actual speed so I ended up getting a speedohealer to recalibrate the speedo.

I did this on my Blackbird years ago. I can't remember exactly how many teeth it was but it was front and back changed to keep the speedo right.

I was planning on just doing the front but that would have ended up with it racking up more miles than it actually had (by my gearing calculations at the time aka Google)

It transformed the Blackbird from a far too fast and heavy touring bike into a far too fast and heavy touring bike that liked to cock it's front wheel when it got the chance.